1. Field of the Invention
The present invention relates to a rotor and a motor.
2. Description of the Related Art
In the conventional practice, motors are used as driving sources of various types of apparatuses and products. For example, the motors are used for business machines, such as printers and copying machines, various kinds of home electric appliances, and power assist sources of vehicles, such as automobiles and power-assisted bicycles. In particular, brushless motors are sometimes used as the driving sources of movable parts with high operation frequency in the light of increased durability and reduced noise.
Known as a type of such a brushless motor is an interior permanent magnet (IPM) motor where a permanent magnet is embedded in a rotor. For example, there is an electric motor in which a plurality of plate-like magnets are radially embedded in a rotor yoke and also each magnet is disposed such that the same poles of adjacent magnets face each other circumferentially.
In this electric motor, disk-like auxiliary permanent magnets are provided at both end faces of the rotor in a direction of a rotating shaft, for the purpose of reducing the magnetic flux that may have leaked from the magnets embedded in the rotor yoke in the direction of the rotating shaft.
The auxiliary permanent magnets in the above-described electric motor are configured such that a plurality of magnetic poles are circularly formed on a surface facing the rotor core. Thus, there is the following problem to be solved. That is, the repulsive force, between the rotor core and the auxiliary permanent magnets, and their mutual demagnetization resistance are varied depending on how the auxiliary permanent magnets are mounted to the rotor core.